With rising concerns over environmental issues, current trends are leaning toward reduced use of chemical herbicides in weed control. For some time it has been known in the prior art to use steam or heated water to try and kill weeds, and a number of devices or machines have been developed to make use of this principle. U.S. Pat. Nos. 5,385,106, 5,927,601, 5,946,851 and 7,100,540, U.S. Patent Application Publication Number 2007/0176316, European Patent Application Number 1695620 and Japanese Patent Document Numbers 7-163285 and 2002-065138 teach examples of such water or steam-based prior art solutions.
However, some of these prior art solutions include use of large equipment and vehicle-based systems that do not lend well to small scale use by individual home owners for personal lawn maintenance, configurations that apply steam or heated water in an above ground context that may inadvertently damage surrounding vegetation or may not adequately treat the subsurface element of the weeds to prevent the unwanted vegetation from re-emerging, and configurations that, while small enough for portable or personal use, require on board electrical sources or combustible fuel to heat and convey the water. Combustion-based tools can be expensive to operate, emit harmful exhaust fumes and present risk of explosion or fire. While battery technology has dramatically improved in recent years, some consumers are hesitant to purchase battery operated yard care tools in view of the potential loss of ability to maintain the battery's original level of charge after repeated uses, leading to reduced performance or need for replacement battery packs.
In U.S. Patent Application Publication 2011/0283609, Applicant previously proposed a solution involving use of compressed air for pressurized injection of heated water into the ground directly to the endosperm of the unwanted vegetation. However, Applicant found that due to variations in soil conditions, pressurized injection of the water beneath the surface can lead to unpredictable results in the size of the ‘kill area’.
As a result, Applicant has moved away from below-ground injection, and has now developed a new apparatus for surface-level application of superheated water in a targeted manner effective for spot treatment of weeds without undesired harm to surrounding grass or other vegetation that the user wishes to leave intact.